An engine obtains power by rotation of a crankshaft caused by combustion of mixture gas in a combustion chamber. However, not all of the mixture gas introduced to the combustion chamber is combusted. A portion of the mixture gas leaks through a gap between a piston and a cylinder into a crankcase. This leaked gas is called blowby gas. Blowby gas as un-combusted fuel gas contains air pollutant in a high concentration. Therefore, discharging it as it is as an exhaust gas into the atmosphere is legally prohibited. Accordingly, an arrangement is provided for returning blowby gas to an intake port side via a PCV (Positive Crankcase Ventilation) channel, so that it is combusted with an amount of newly supplied mixture gas in the combustion chamber and then discharged into the atmosphere.
PTL 1 discloses an arrangement wherein gas inlets for introducing blowby gas are opened in pipe walls of a plurality of intake pipes and a gas introducing channel for distributing the blowby gas is connected to the gas inlets via a gas introducing chamber housing. The lower face of the inside of the gas introducing chamber housing is inclined downwards toward the gas inlets and the lower edge of the lower face is located at a position higher than the intake pipe side of the gas inlets. With this arrangement, water present inside the gas introducing chamber housing is caused to flow along the lower face of the inside of the gas introducing chamber housing to reach the gas inlets of the intake pipes and and then to flow along the lower edges of the gas inlets to enter the intake pipes.
PTL 2 discloses an arrangement in which a heating pipe is rigidly attached to an outer circumference of an insertion pipe constituting a portion of a PCV channel and engine cooling water is caused to flow inside the heating pipe. As the engine cooling water flowing inside the heating pipe has a high temperature, this raises the temperature of blowby gas flowing inside the insertion pipe, thus preventing freezing of steam contained in the blowby gas flowing in the PCV channel.